By first light, Waldemarin and I, with Senhor Japão at the helm of our small boat, are already puttering over the Rio Negro’s olive green water, a highway that meanders through a mosaic of ponds and lakes, each teeming with fish of many species. Waldemarin explains that the otters maintain a network of dens, camps and resting places that they visit and clean regularly. Senhor Japão is expert at spotting the otters’ entrances, even though they are often disguised by overhanging vegetation. The entrance tunnel, often 15 feet long, leads to a grand chamber with a floor area the size of a suburban living room, large enough to accommodate an otter family. He nudges the boat into a steep, crumbling clay bank, striated with vertical claw marks where the otters had clearly climbed out of the water. Senhor Japão points to a dark opening the size of a squashed car tire just below the lip of the bank. The mud around the entrance is still wet; the otters must have just left.

Behind us comes a snort, and we all spin around in the canoe to see a streamlined head, whiskered like a bottlebrush, cutting an arrowhead wake. Snorting in what sounds like agitation, the otter stops to investigate us, craning its head, standing up in the water for a better view. Waldemarin looks for the cream-colored markings on its neck that are as individual as a human’s fingerprints, but before she can make an identification, the giant otter ducks, dives and disappears.

Waldemarin tells me that the usually inquisitive otters are acting uncharacteristically wary; soon we find out why. At the entrance to another den, Senhor Japão points out a log that, at closer examination, turns out to be a large caiman, a species of crocodile. “The otters must already have cubs,” Waldemarin says. The caiman has been lured by the promise of food.

Big caimans are not the otters’ only predator. Their velvety chocolate-brown fur is among the finest in the world, and the high price it once fetched on international markets led to decades of relentless and uncontrolled hunting by man. Throughout their original range, from the Orinoco basin in Colombia and Venezuela to the Pantanal and northern Argentina, the curious otters, often approaching canoes in entire families, were an easy target for hunters who sought their pelts.

Official statistics only hint at the true extent of the slaughter: during a seven-year period in the 1960s, Brazil exported more than 40,000 pelts. But these figures don’t account for a thriving illegal trade or the fact that more specimens were killed than recovered. Alarmed by the rapid disappearance of the giant otters, several South American countries granted them legal protection in the mid-1970s. By then, the Convention on International Trade in Endangered Species (CITES) had outlawed trade in otter skins, but clandestine commercial hunting continued, particularly in remote areas of the Amazon and Venezuela, with most pelts smuggled out via Colombia. As the numbers of giant otters in the wild plummeted, the price for their skins increased, and by the late ’70s, they were fetching $250 each. In 1979, Venezuela was the last country to ban the hunting of otters. Since then, the animals have returned in significant numbers— to about 5,000—though they remain on the endangered list of the World Conservation Union (WCU).

Giant otters live in locally dense populations scattered through pockets of remote habitat. Outside the Pantanal, their other stronghold is Manu Biosphere Reserve, a river basin the size of Massachusetts, in southeastern Peru. Here the Frankfurt Zoological Society has coordinated a number of systematic field studies over the past dozen years.

Martha Brecht Munn, a WCU biologist, observed a family of otters in Peru hunting an anaconda, among the world’s largest snakes. “Two or more otters would bite and hold the snake at different places on its body,” she wrote in Animal Kingdom magazine. “They would then thrash it against a fallen tree trunk and engage in what looked like a tug-ofwar with an animated fire hose.” In a group, they could also make short work of a five-foot-long caiman, devouring the reptile—skull, bones and all—in 45 minutes. Most of the time, however, giant otters prefer fish. Brecht Munn wrote that they seem to hunt together as much for camaraderie as to subdue large prey.

She also described some cubs’ first swimming lessons: “When [they] were about two weeks old, their [parents] carried them outside one by one . . . and dropped them into the water at the den entrance. The cubs were about the size of a loaf of bread, their eyes still closed, and they bobbed about helplessly.” All the adult otters circled the cubs to protect them from loitering caimans.

Another predawn start in the pantanal, and this time I’m searching for otters with Marion Kallerhoff, a South African wildlife specialist here to work with scientists studying jaguars, hyacinth macaws and giant otters. As we push off into the dark water, I scan the banks with my flashlight; the eyes of caimans light up like reflective highway markers. After an hour of paddling our canoes, we stop, a half mile across the river from the most likely otter dens, to await the daylight. The foghorn-like humming of curassow birds begins to echo from the forest, and jabiru storks cross against the gray sky like small aircraft. But first up are the mosquitoes. Because otters have an excellent sense of smell, Kallerhoff suggested we not use any insect repellent. Now I cringe against the onslaught. Then, all of sudden, I forget the insects’ annoying whine.

Across the river, a whiskery face pops up with a nostrilclearing snort, then another face appears, followed by yet another. A family of giant otters has just emerged from its den and begins to feed with the splashy exuberance of kids in a backyard swimming pool. I ease my canoe back into the river, quietly paddle upstream, then drift down, still as a log.

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